1. Field of the Invention
This invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having the easy magnetization axis in the perpendicular direction to the surface of the medium and very high anisotropic energy.
2. Description of the Prior Arts
Recently, in place of a so-called in-plane type magnetic recording system of magnetizing the magnetic recording medium in the plane direction of the surface of the medium, a perpendicular magnetic recording system of magnetizing the magnetic recording medium in the perpendicular direction to the surface of the medium is being watched with keen interest and one of such systems is disclosed in, for example, Japanese Patent Publication (OPI) No. 134,706/'77.
The perpendicular type magnetic recording system has the feature that the demagnetization field becomes lower as the recording density becomes higher and hence the system is essentially suitable for super high density recording.
A medium used for the perpendicular magnetic recording system is required to have a large magnetic anisotropy in the perpendicular direction to the surface of the medium and a large coercive force and as a medium meeting these factors, it is known that the Co-Cr layer formed by high frequency sputtering method is excellent.
However, in the case of forming the Co-Cr layer by a sputtering method, it is very difficult to utilize high speed magnetron sputtering owing to the ferromagnetic property of the target itself.